How to ensure seed quality

Good quality seeds (left) are uniform in size, full, and plump; while poor quality seeds (right) are often discolored.Seed is the foundation of any rice crop. It must be grown, harvested, and processed correctly for best yield and quality results.

Sowing good quality seeds leads to lower seed rate, better emergence (>70%), more uniformity, less replanting, and vigorous early growth which helps to increase resistance to insects and diseases, and decrease weeds. As a result, yield can increase by 5−20%.

While different countries have different standards for seed quality the following factors are used to classify rice seeds:

Seed lot purity

Impurities refer to the degree of contamination caused by (1) weed seeds, (2) seeds of other crops or species, and (3) inert material such as stones, dirt, or twigs. It is expressed as a percentage, by weight.

To measure seed lot purity:

Randomly select a seed sample. 100 g is a good sample size.

Weigh the sample. [A]

Remove all of the weed and other crop seeds.

Weigh the removed weed and other crop seed matter. [B]

Compute the weed percentage using the following formula:

Weigh the inert matter removed from the sample [C], the inert matter percentage is calculated using the formula:

Discoloration

Fungi, bacteria, and environmental conditions such as high humidity and temperature (i.e. 27−35°) cause discoloration.

Other rice diseases do not produce consistent discoloration. Any seed having more than 0.5% differently colored or spotted seed surface is considered discolored. Discoloration can occur on fully or partially filled or empty grains.

Seed vigor refers to the seed’s level of activity and performance during germination and seedling emergence. The ability of the germinating seed to continue to grow and survive is important in crop establishment.

Seeds that are low in vigor generally produce weak seedlings that are susceptible to environmental stresses. On the other hand, seeds that are high in vigor produce early and uniform stand, which gives them a competitive advantage against environmental stresses.

Moisture content

Moisture content is the amount of water in the rice grain.

It influences the life and vigor of the seed. The amount of moisture should be less than 14%, and preferably less than 12% for extended storage times.

High quality seeds are free from weed seeds, seed-borne diseases, insects, pathogens, and other extraneous matter. They should also be free from various types of mechanical injury that reduce germination and seedling vigor.